Download The Immune System

The body’s defense mechanism against
attack from infectious diseases, bites,
viruses, etc.
 Anything (organism) that causes a disease
is called a pathogen

› Most commonly infectious organisms are called
pathogens
› Some pathogens cause disease by producing
poisons called toxins, while some pathogens
such as worms will burrow into muscle tissue
and other cells and destroy the tissues

The immune system consists of cells and
chemicals that protect the body against
invasion by foreign substances and
maintain its general health.

Immune System


Disease is when the
infection causes
damage to the
individual’s vital
functions or systems.
Not all infections
lead to a disease!

Some disease can be
passed from animals
to humans= zoonotic

Direct Contact (person to
person)
› Vertical: kissing, sneezing,
sexual contact, etc.
› Horizontal: placenta, breast
milk

Indirect Contact: requires
a carrier or vector for the
disease to be spread
› Air, objects, etc. can be
vectors and carry infectious
agents from one person to
another, thus transmitting the
disease
› Water and Food can be a cause for the
spread of disease in areas where sanitation
issues are a problem, such as amebic
dysentery from contaminated water and
Salmonella from eggs, turkey, etc.
› Animal Bites are also concern for the
transmission of disease, because of the fact
that animals can be a vector for many viruses,
i.e. bubonic plague was spread by fleas, Lyme
disease is spread by ticks, rabies is spread in
the saliva of infected mammals, such as dogs

First Line of Defense:
› Tears, mucus, skin, hair, nails, cilia (nose
hairs), etc. (Much like a fence surrounds a
house to protect burglars from entering)
› Non-specific because the defenses do not
care what type of pathogen tries to enter
› Your skin acts as a barrier to protect your
internal organs from ANY pathogen trying to
enter

Nonspecific immune defenses protect
against foreign cells or matter without
having to recognize their specific
identities.
› Include defenses at the body surfaces and
defense to injury
 inflammation
Respiratory System
Integumentary System

Poses both a physical and a chemical
barrier to invading organisms
› Sweat
› Sebum

Act to maintain the skins environment

Provides mechanical and chemical
barriers to infection
› Ciliated mucous membranes filter incoming air
of impurities
› Mucus entraps foreign material and has
antiseptic properties

Prevent many pathogens from multiplying
Gastrointestinal Tract
› Saliva
› Hydrochloric acid

Other mechanisms that can help to wash
foreign substances out of the body
Others
› Urine
› Tears

Other substances are also involved in
protecting the body from disease.
› Histamines and prostaglandins produce
vasodilation and inflammation.
 Increase the local vascular permeability,
bringing more leukocytes and phagocytes to
the area to combat infection
 Pyrogens are released by the invading bacteria and
the defending leukocytes causing fever (pyr – fire or
heat)
 Fever activates the phagocytic action of the immune
system

Specific immunity is the response of the
defenses of the body to specific
substances that are recognized as
harmful.
› Antigens
 Can be foreign to the body, such as bacteria,
viruses, and parasites, or can be part of the
body's immune mechanism

White blood cells called lymphocytes are
the essential cells in specific immune
defense.
› B cells
 Formed and mature in the bone marrow
 Produce humoral immunity
 antibodies
› T cells
 Made in bone marrow, but mature in the Thymus
 Cellular immunity
› Null Cells
 Natural killer cells
 Fight tumor cells

Immunity can develop passively or
actively.
› Passive immunity develops when antibodies
are transferred from mother to young, or are
injected into an animal
› Active immunity is aquired by vaccination or
by natural infection with a microorganism.
 Vaccination is the administration of an antigen
to stimulate a protective immune response
against an infectious agent
**The immune system plays an ACTIVE role in
defense**

There are two major types of immune
system problems:
› Weakness or deficiency in the effectiveness
of the system
› Excessively strong reaction by the system

These problems can arise from congenital
factors in which blood cells are insufficient
or inefective.
› Severe Combined Immunodeficiency Disease
 Fail to develop mature T and B cells
› Cyclic Hematopoiesis
 Occurs in Collies – cyclic fluctuations in white blood cells
› Feline Leukemia Virus, Feline Immunodeficiency
Virus
 Suppress the immune system

In some situations, the immune system
response to an antigen produces
excessive inflammatory reactions and
other complications
› Bees
 Anaphylaxis
 Swelling, airway blockage, and tachycardia

Greatest problem is autoimmune disease
› Immune system cannot distinguish between
foreign antigens and those of its own cells
 Rheumatoid arthritis